The first two verbs are in the aorist tense, marking definite acts; the third is in the imperfect, marking the continued gracious agency of God, and possibly the simultaneousness of His work with that of the two preachers. God was giving the increase while we planted and watered. There is a parallel in the simultaneous work of Satan with that of the preachers of the word as indicated by the continuous presents in Matthew 13:19. See note there.